Intro to EKGs

Question 1

What do leads detect?

Answer 1

Vector of depolarization of myocardial cells

Question 2

Characteristics of the P wave?

Answer 2

■ sequential depolarization of the RA / LA
● biphasic in V1 (sometimes III)
●

Question 3

What is the PR interval? Normal time?

Answer 3

■ atrial depolarization time + conduction through AV node, Bundle of His, and bundle branches/onset of
atrial depolarization → onset of ventricular depolarization
● 0.12 sec. - 0.2 sec

Question 4

What is the QRS complex?

Answer 4

■ simultaneous activation of both the RV and LV

Question 5

Duration of QRS?

Answer 5

■ 0.06-0.1 sec

Question 6

What is the ST segment?

Answer 6

■ time between ventricular depolarization / repolarization

Question 7

What is the J point?

Answer 7

■ junction between termination of QRS and beginning of ST

Question 8

What is the T wave?

Answer 8

■ repolarization of the ventricles

Question 9

In which direction do the ventricles repolarize?

Answer 9

● occurs epicardium → endocardium (opposite direction of depolarization)

Question 10

What is the QT interval? Length?

Answer 10

• Start of ventricular depolarization to end of ventricular repolarization, which encompasses all of electrical events in ventricles in one cardiac cycle
  ● typically 40% of cycle

Question 11

Which are the anterior leads?

Answer 11

V1, V2, V3, V4

Question 12

Which are the inferior leads?

Answer 12

II, III, aVF

Question 13

Which are the left lateral leads?

Answer 13

I, aVL, V5, V6

Question 14

Which are the right leads?

Answer 14

aVR, V1

Question 15

What is normal paper speed? Calibration?

Answer 15

speed=25.0 mm/s

calibration= 10.0 mm/mV

Question 16

What do large and small boxes indicate on EKG?

Answer 16

■ 1 small box = 0.1 cm, 0.04 sec, 0.1mV

■ 1 large box = 0.5 cm, 0.2 sec, 0.5 mV

Question 17

What does axis deviation suggest?

Answer 17

Change in heart size, shift in heart position, or blockage in electrical system

Question 18

Requirements for sinus rhythm?

Answer 18

1. Normal identical P waves before every QRS: II /IV

2. Narrow QRS (

Question 19

What is a normal P wave?

Answer 19

○ upright in leads I and II

○ inverted in aVR

Question 20

Characteristics of Sinus arrhythmia?

Answer 20

○ regularly irregular

○ HR accelerates w/ inspiration and slows w/ expiration

Question 21

Atrial flutter characteristics?

Answer 21

■ regularly irregular
■ “saw tooth” p waves
■ atrial rate typically 250-350 bpm

Question 22

A fib characteristics?

Answer 22

■ irregularly irregular (no pattern)

■ undulating baseline/fibrillatory, no visible p waves

Question 23

How to tell if axis is normal?

Answer 23

■ + lead 1

■ + lead aVF

Question 24

How to tell if LAD?

Answer 24

■ + lead 1

■ - lead aVF

Question 25

How to tell if RAD

Answer 25

■ - lead 1

■ + lead aVF

Question 26

How to use isoelectric lead to find axis?

Answer 26

■ find isoelectric limb lead
■ identify perpendicular lead to isoelectric lead to approximate axis decide which direction of that lead you
will use fo the vector based on whether lead I and aVF are + or -

Question 27

What are normal interval durations?

Answer 27

○ PR interval: 0.12 - 0.2 sec.
○ QRS interval: 0.06 - 0.1 sec
○ QT interval: 0.2 - 0.4 sec

Question 28

RBBB characteristics?

Answer 28

■ QRS widened > 0.12 sec.
■ RSR’ in leads V1 and V2 w/ ST segment depression and T wave inversion
■ reciprocal changes in leads V5, V6, I, aVL

Question 29

LBBB characteristics?

Answer 29

■ QRS widened > 0.12 sec.

■ broad or notched R wave w/ prolonged upstroke in leads V5, V6, I, and aVL

Question 30

Left anterior hemiblock characteristics?

Answer 30

■ normal QRS duration and no ST segment or T wave changes
■ LAD > -30°
■ no other cause of LAD present

Question 31

Left posterior hemiblock characteristics?

Answer 31

■ normal QRS duration and no ST segment or T wave changes
■ RAD
■ no other cause of RAD present

Question 32

LAE Characteristics?

Answer 32

Commonly caused by mitral valve disease
● 2nd half (negative portion) of P wave amplitude ≥ 1 mm/1box below isoelectric line in V1
○ duration of 2nd half of P wave ≥ 0.04 sec (1 box)
● no significant axis deviation

Question 33

RAE characteristics?

Answer 33

commonly caused by severe lung disease
● P wave amplitude> 2.5mm/2.5boxes tall in leads II, III, and aVF (inferior leads)
○ note: no change in duration of P wave

Question 34

LVH characteristics?

Answer 34

commonly caused by systemic HTN, valvular disease
● amplitude R V5/V6 + S in V1/V2 > 35
● amplitude of R wave in aVL > 13 mm
● left axis deviation > -15° is also present

Question 35

RVH characteristics?

Answer 35

caused by COPD, uncorrected congenital heart disease
● R axis deviation> +100°
● R wave is > S wave in V1 and S wave > R wave in V6